My husband said he shut down all and any sexual thoughts of other women when he became committed to me, so I disagree with you. He also quit using porn for me. He used it when he was not having any sex with his ex wife for two years. Sure, many married men AND women may fantasize, but that's not the issue necessarily. You cheated 20 times.. your fiance deserves to know. You are not doing right by her at all in this matter. And if she was so important to you, why did you cheat 20 times?

She is marrying someone who is lying to her, or at least who is omitting the full truth. You have to man up to your actions, be honest with her, and let HER choose. It's just not right.

At the very least, don't get married if you cannot tell her the full truth. Delay or cancel. You want to change, you need to see a therapist. It won't simply stop because you want it to. You get a thrill from this, and then you get bored. It's a problem. What happens when you're bored after 5, 10, 15 years of marriage? You're cheating again?